Wireless communication systems are widely spread all over the world to provide various types of communication services such as voice or data. The wireless communication system is designed for the purpose of providing reliable communication to a plurality of users irrespective of their locations and mobility. However, a wireless channel has an abnormal characteristic such as a fading phenomenon caused by a path loss, noise, and a multi-path, an inter-symbol interference (ISI), a Doppler effect caused by mobility of a mobile station (MS), etc. Therefore, various techniques have been developed to overcome the abnormal characteristic of the wireless channel and to increase reliability of wireless communication.
Meanwhile, the wireless communication system is a cellular system. The cellular system provides a communication service by dividing a service area into a plurality of cells to overcome a restriction of the service area and a limitation of capability for accommodating users. However, users located in a cell edge experience inter-cell interference (ICI) due to an interference signal from a neighbor cell. A base station (BS) also experiences the ICI due to the interference signal from the neighbor cell. The ICI is a primary cause of restricting performance of the wireless communication system. The ICI may result in depletion of transmit (Tx) signals and receive (Rx) signals of the users located in the cell edge, decrease in performance, waste of Tx power, etc. This causes a problem in terms of supporting of various services for the users located in the cell edge, maintaining of quality of service (QoS), and cell coverage. Therefore, the next-generation wireless communication system requires to solve the ICI problem and to improve system performance.
A fractional frequency reuse (FFR) scheme is used as one of methods for solving the ICI problem. The FFR scheme divides a full frequency band into a plurality of frequency partitions (FPs), and allocates the FPs to respective cells. According to the FFR scheme, different FPs can be allocated between neighbor cells, and the same FP can be allocated between cells spaced apart from each another. Therefore, ICI can be reduced, and performance of an MS located in a cell edge can be increased.
A method of controlling uplink power is another method for solving the ICI problem. The power control method regulates Tx power so that an uplink signal can be transmitted with the lowest power level while maintaining QoS of the wireless communication system to some extent. MSs located near a cell edge in the cellular system are significantly affected by a path loss, the ICI, etc. The MS has to transmit an uplink signal by determining proper Tx power by avoiding decrease of QoS in association with the path loss while avoiding interference to a neighbor cell.
Accordingly, there is a need for a method of controlling uplink power to effectively regulate ICI when using an FFR scheme.